/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.base;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.regex.Pattern;
import javax.annotation.Nullable;

/**
 * Static utility methods pertaining to {@code Predicate} instances.
 *
 * <p>
 * All methods returns serializable predicates as long as they're given serializable parameters.
 *
 * <p>
 * See the Guava User Guide article on
 * <a href="https://github.com/google/guava/wiki/FunctionalExplained">the use of
 * {@code Predicate}</a>.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@GwtCompatible(emulated = true)
public final class Predicates {
    private Predicates() {}

    // TODO(kevinb): considering having these implement a VisitablePredicate
    // interface which specifies an accept(PredicateVisitor) method.

    /**
     * Returns a predicate that always evaluates to {@code true}.
     */
    @GwtCompatible(serializable = true)
    public static <T> Predicate<T> alwaysTrue() {
        return ObjectPredicate.ALWAYS_TRUE.withNarrowedType();
    }

    /**
     * Returns a predicate that always evaluates to {@code false}.
     */
    @GwtCompatible(serializable = true)
    public static <T> Predicate<T> alwaysFalse() {
        return ObjectPredicate.ALWAYS_FALSE.withNarrowedType();
    }

    /**
     * Returns a predicate that evaluates to {@code true} if the object reference being tested is
     * null.
     */
    @GwtCompatible(serializable = true)
    public static <T> Predicate<T> isNull() {
        return ObjectPredicate.IS_NULL.withNarrowedType();
    }

    /**
     * Returns a predicate that evaluates to {@code true} if the object reference being tested is
     * not null.
     */
    @GwtCompatible(serializable = true)
    public static <T> Predicate<T> notNull() {
        return ObjectPredicate.NOT_NULL.withNarrowedType();
    }

    /**
     * Returns a predicate that evaluates to {@code true} if the given predicate evaluates to
     * {@code false}.
     */
    public static <T> Predicate<T> not(Predicate<T> predicate) {
        return new NotPredicate<T>(predicate);
    }

    /**
     * Returns a predicate that evaluates to {@code true} if each of its components evaluates to
     * {@code true}. The components are evaluated in order, and evaluation will be "short-circuited"
     * as soon as a false predicate is found. It defensively copies the iterable passed in, so
     * future changes to it won't alter the behavior of this predicate. If {@code
     * components} is empty, the returned predicate will always evaluate to {@code
     * true}.
     */
    public static <T> Predicate<T> and(Iterable<? extends Predicate<? super T>> components) {
        return new AndPredicate<T>(defensiveCopy(components));
    }

    /**
     * Returns a predicate that evaluates to {@code true} if each of its components evaluates to
     * {@code true}. The components are evaluated in order, and evaluation will be "short-circuited"
     * as soon as a false predicate is found. It defensively copies the array passed in, so future
     * changes to it won't alter the behavior of this predicate. If {@code
     * components} is empty, the returned predicate will always evaluate to {@code
     * true}.
     */
    public static <T> Predicate<T> and(Predicate<? super T>... components) {
        return new AndPredicate<T>(defensiveCopy(components));
    }

    /**
     * Returns a predicate that evaluates to {@code true} if both of its components evaluate to
     * {@code true}. The components are evaluated in order, and evaluation will be "short-circuited"
     * as soon as a false predicate is found.
     */
    public static <T> Predicate<T> and(Predicate<? super T> first, Predicate<? super T> second) {
        return new AndPredicate<T>(Predicates.<T>asList(checkNotNull(first), checkNotNull(second)));
    }

    /**
     * Returns a predicate that evaluates to {@code true} if any one of its components evaluates to
     * {@code true}. The components are evaluated in order, and evaluation will be "short-circuited"
     * as soon as a true predicate is found. It defensively copies the iterable passed in, so future
     * changes to it won't alter the behavior of this predicate. If {@code
     * components} is empty, the returned predicate will always evaluate to {@code
     * false}.
     */
    public static <T> Predicate<T> or(Iterable<? extends Predicate<? super T>> components) {
        return new OrPredicate<T>(defensiveCopy(components));
    }

    /**
     * Returns a predicate that evaluates to {@code true} if any one of its components evaluates to
     * {@code true}. The components are evaluated in order, and evaluation will be "short-circuited"
     * as soon as a true predicate is found. It defensively copies the array passed in, so future
     * changes to it won't alter the behavior of this predicate. If {@code
     * components} is empty, the returned predicate will always evaluate to {@code
     * false}.
     */
    public static <T> Predicate<T> or(Predicate<? super T>... components) {
        return new OrPredicate<T>(defensiveCopy(components));
    }

    /**
     * Returns a predicate that evaluates to {@code true} if either of its components evaluates to
     * {@code true}. The components are evaluated in order, and evaluation will be "short-circuited"
     * as soon as a true predicate is found.
     */
    public static <T> Predicate<T> or(Predicate<? super T> first, Predicate<? super T> second) {
        return new OrPredicate<T>(Predicates.<T>asList(checkNotNull(first), checkNotNull(second)));
    }

    /**
     * Returns a predicate that evaluates to {@code true} if the object being tested
     * {@code equals()} the given target or both are null.
     */
    public static <T> Predicate<T> equalTo(@Nullable T target) {
        return (target == null) ? Predicates.<T>isNull() : new IsEqualToPredicate<T>(target);
    }

    /**
     * Returns a predicate that evaluates to {@code true} if the object being tested is an instance
     * of the given class. If the object being tested is {@code null} this predicate evaluates to
     * {@code false}.
     *
     * <p>
     * If you want to filter an {@code Iterable} to narrow its type, consider using
     * {@link com.google.common.collect.Iterables#filter(Iterable, Class)} in preference.
     *
     * <p>
     * <b>Warning:</b> contrary to the typical assumptions about predicates (as documented at
     * {@link Predicate#apply}), the returned predicate may not be <i>consistent with equals</i>.
     * For example, {@code instanceOf(ArrayList.class)} will yield different results for the two
     * equal instances {@code Lists.newArrayList(1)} and {@code Arrays.asList(1)}.
     */
    @GwtIncompatible // Class.isInstance
    public static Predicate<Object> instanceOf(Class<?> clazz) {
        return new InstanceOfPredicate(clazz);
    }

    /**
     * Returns a predicate that evaluates to {@code true} if the class being tested is assignable
     * <b>TO</b> {@code clazz}, that is, if it is a <b>subtype</b> of {@code clazz}. Yes, this
     * method is named very incorrectly! Example:
     * 
     * <pre>
     * {
     *     &#64;code
     *
     *     List<Class<?>> classes = Arrays.asList(Object.class, String.class, Number.class, Long.class);
     *     return Iterables.filter(classes, assignableFrom(Number.class));
     * }
     * </pre>
     *
     * The code above returns {@code Number.class} and {@code Long.class}, <b>not</b> {@code
     * Number.class} and {@code Object.class} as the name implies!
     *
     * <p>
     * The returned predicate does not allow null inputs.
     *
     * @deprecated Use the correctly-named method {@link #subtypeOf} instead.
     * @since 10.0
     */
    @GwtIncompatible // Class.isAssignableFrom
    @Beta
    @Deprecated
    public static Predicate<Class<?>> assignableFrom(Class<?> clazz) {
        return subtypeOf(clazz);
    }

    /**
     * Returns a predicate that evaluates to {@code true} if the class being tested is assignable to
     * (is a subtype of) {@code clazz}. Example:
     * 
     * <pre>
     * {
     *     &#64;code
     *
     *     List<Class<?>> classes = Arrays.asList(Object.class, String.class, Number.class, Long.class);
     *     return Iterables.filter(classes, subtypeOf(Number.class));
     * }
     * </pre>
     *
     * The code above returns an iterable containing {@code Number.class} and {@code Long.class}.
     *
     * @since 20.0 (since 10.0 under the incorrect name {@code assignableFrom})
     */
    @GwtIncompatible // Class.isAssignableFrom
    @Beta
    public static Predicate<Class<?>> subtypeOf(Class<?> clazz) {
        return new SubtypeOfPredicate(clazz);
    }

    /**
     * Returns a predicate that evaluates to {@code true} if the object reference being tested is a
     * member of the given collection. It does not defensively copy the collection passed in, so
     * future changes to it will alter the behavior of the predicate.
     *
     * <p>
     * This method can technically accept any {@code Collection<?>}, but using a typed collection
     * helps prevent bugs. This approach doesn't block any potential users since it is always
     * possible to use {@code Predicates.<Object>in()}.
     *
     * @param target the collection that may contain the function input
     */
    public static <T> Predicate<T> in(Collection<? extends T> target) {
        return new InPredicate<T>(target);
    }

    /**
     * Returns the composition of a function and a predicate. For every {@code x}, the generated
     * predicate returns {@code predicate(function(x))}.
     *
     * @return the composition of the provided function and predicate
     */
    public static <A, B> Predicate<A> compose(Predicate<B> predicate, Function<A, ? extends B> function) {
        return new CompositionPredicate<A, B>(predicate, function);
    }

    /**
     * Returns a predicate that evaluates to {@code true} if the {@code CharSequence} being tested
     * contains any match for the given regular expression pattern. The test used is equivalent to
     * {@code Pattern.compile(pattern).matcher(arg).find()}
     *
     * @throws IllegalArgumentException if the pattern is invalid
     * @since 3.0
     */
    @GwtIncompatible // Only used by other GWT-incompatible code.
    public static Predicate<CharSequence> containsPattern(String pattern) {
        return new ContainsPatternFromStringPredicate(pattern);
    }

    /**
     * Returns a predicate that evaluates to {@code true} if the {@code CharSequence} being tested
     * contains any match for the given regular expression pattern. The test used is equivalent to
     * {@code pattern.matcher(arg).find()}
     *
     * @since 3.0
     */
    @GwtIncompatible(value = "java.util.regex.Pattern")
    public static Predicate<CharSequence> contains(Pattern pattern) {
        return new ContainsPatternPredicate(new JdkPattern(pattern));
    }

    // End public API, begin private implementation classes.

    // Package private for GWT serialization.
    enum ObjectPredicate implements Predicate<Object> {
        /** @see Predicates#alwaysTrue() */
        ALWAYS_TRUE {
            @Override
            public boolean apply(@Nullable Object o) {
                return true;
            }

            @Override
            public String toString() {
                return "Predicates.alwaysTrue()";
            }
        },
        /** @see Predicates#alwaysFalse() */
        ALWAYS_FALSE {
            @Override
            public boolean apply(@Nullable Object o) {
                return false;
            }

            @Override
            public String toString() {
                return "Predicates.alwaysFalse()";
            }
        },
        /** @see Predicates#isNull() */
        IS_NULL {
            @Override
            public boolean apply(@Nullable Object o) {
                return o == null;
            }

            @Override
            public String toString() {
                return "Predicates.isNull()";
            }
        },
        /** @see Predicates#notNull() */
        NOT_NULL {
            @Override
            public boolean apply(@Nullable Object o) {
                return o != null;
            }

            @Override
            public String toString() {
                return "Predicates.notNull()";
            }
        };

        @SuppressWarnings("unchecked") // safe contravariant cast
        <T> Predicate<T> withNarrowedType() {
            return (Predicate<T>) this;
        }
    }

    /** @see Predicates#not(Predicate) */
    private static class NotPredicate<T> implements Predicate<T>, Serializable {
        final Predicate<T> predicate;

        NotPredicate(Predicate<T> predicate) {
            this.predicate = checkNotNull(predicate);
        }

        @Override
        public boolean apply(@Nullable T t) {
            return !predicate.apply(t);
        }

        @Override
        public int hashCode() {
            return ~predicate.hashCode();
        }

        @Override
        public boolean equals(@Nullable Object obj) {
            if (obj instanceof NotPredicate) {
                NotPredicate<?> that = (NotPredicate<?>) obj;
                return predicate.equals(that.predicate);
            }
            return false;
        }

        @Override
        public String toString() {
            return "Predicates.not(" + predicate + ")";
        }

        private static final long serialVersionUID = 0;
    }

    private static final Joiner COMMA_JOINER = Joiner.on(',');

    /** @see Predicates#and(Iterable) */
    private static class AndPredicate<T> implements Predicate<T>, Serializable {
        private final List<? extends Predicate<? super T>> components;

        private AndPredicate(List<? extends Predicate<? super T>> components) {
            this.components = components;
        }

        @Override
        public boolean apply(@Nullable T t) {
            // Avoid using the Iterator to avoid generating garbage (issue 820).
            for (int i = 0; i < components.size(); i++) {
                if (!components.get(i).apply(t)) {
                    return false;
                }
            }
            return true;
        }

        @Override
        public int hashCode() {
            // add a random number to avoid collisions with OrPredicate
            return components.hashCode() + 0x12472c2c;
        }

        @Override
        public boolean equals(@Nullable Object obj) {
            if (obj instanceof AndPredicate) {
                AndPredicate<?> that = (AndPredicate<?>) obj;
                return components.equals(that.components);
            }
            return false;
        }

        @Override
        public String toString() {
            return "Predicates.and(" + COMMA_JOINER.join(components) + ")";
        }

        private static final long serialVersionUID = 0;
    }

    /** @see Predicates#or(Iterable) */
    private static class OrPredicate<T> implements Predicate<T>, Serializable {
        private final List<? extends Predicate<? super T>> components;

        private OrPredicate(List<? extends Predicate<? super T>> components) {
            this.components = components;
        }

        @Override
        public boolean apply(@Nullable T t) {
            // Avoid using the Iterator to avoid generating garbage (issue 820).
            for (int i = 0; i < components.size(); i++) {
                if (components.get(i).apply(t)) {
                    return true;
                }
            }
            return false;
        }

        @Override
        public int hashCode() {
            // add a random number to avoid collisions with AndPredicate
            return components.hashCode() + 0x053c91cf;
        }

        @Override
        public boolean equals(@Nullable Object obj) {
            if (obj instanceof OrPredicate) {
                OrPredicate<?> that = (OrPredicate<?>) obj;
                return components.equals(that.components);
            }
            return false;
        }

        @Override
        public String toString() {
            return "Predicates.or(" + COMMA_JOINER.join(components) + ")";
        }

        private static final long serialVersionUID = 0;
    }

    /** @see Predicates#equalTo(Object) */
    private static class IsEqualToPredicate<T> implements Predicate<T>, Serializable {
        private final T target;

        private IsEqualToPredicate(T target) {
            this.target = target;
        }

        @Override
        public boolean apply(T t) {
            return target.equals(t);
        }

        @Override
        public int hashCode() {
            return target.hashCode();
        }

        @Override
        public boolean equals(@Nullable Object obj) {
            if (obj instanceof IsEqualToPredicate) {
                IsEqualToPredicate<?> that = (IsEqualToPredicate<?>) obj;
                return target.equals(that.target);
            }
            return false;
        }

        @Override
        public String toString() {
            return "Predicates.equalTo(" + target + ")";
        }

        private static final long serialVersionUID = 0;
    }

    /** @see Predicates#instanceOf(Class) */
    @GwtIncompatible // Class.isInstance
    private static class InstanceOfPredicate implements Predicate<Object>, Serializable {
        private final Class<?> clazz;

        private InstanceOfPredicate(Class<?> clazz) {
            this.clazz = checkNotNull(clazz);
        }

        @Override
        public boolean apply(@Nullable Object o) {
            return clazz.isInstance(o);
        }

        @Override
        public int hashCode() {
            return clazz.hashCode();
        }

        @Override
        public boolean equals(@Nullable Object obj) {
            if (obj instanceof InstanceOfPredicate) {
                InstanceOfPredicate that = (InstanceOfPredicate) obj;
                return clazz == that.clazz;
            }
            return false;
        }

        @Override
        public String toString() {
            return "Predicates.instanceOf(" + clazz.getName() + ")";
        }

        private static final long serialVersionUID = 0;
    }

    /** @see Predicates#subtypeOf(Class) */
    @GwtIncompatible // Class.isAssignableFrom
    private static class SubtypeOfPredicate implements Predicate<Class<?>>, Serializable {
        private final Class<?> clazz;

        private SubtypeOfPredicate(Class<?> clazz) {
            this.clazz = checkNotNull(clazz);
        }

        @Override
        public boolean apply(Class<?> input) {
            return clazz.isAssignableFrom(input);
        }

        @Override
        public int hashCode() {
            return clazz.hashCode();
        }

        @Override
        public boolean equals(@Nullable Object obj) {
            if (obj instanceof SubtypeOfPredicate) {
                SubtypeOfPredicate that = (SubtypeOfPredicate) obj;
                return clazz == that.clazz;
            }
            return false;
        }

        @Override
        public String toString() {
            return "Predicates.subtypeOf(" + clazz.getName() + ")";
        }

        private static final long serialVersionUID = 0;
    }

    /** @see Predicates#in(Collection) */
    private static class InPredicate<T> implements Predicate<T>, Serializable {
        private final Collection<?> target;

        private InPredicate(Collection<?> target) {
            this.target = checkNotNull(target);
        }

        @Override
        public boolean apply(@Nullable T t) {
            try {
                return target.contains(t);
            } catch (NullPointerException e) {
                return false;
            } catch (ClassCastException e) {
                return false;
            }
        }

        @Override
        public boolean equals(@Nullable Object obj) {
            if (obj instanceof InPredicate) {
                InPredicate<?> that = (InPredicate<?>) obj;
                return target.equals(that.target);
            }
            return false;
        }

        @Override
        public int hashCode() {
            return target.hashCode();
        }

        @Override
        public String toString() {
            return "Predicates.in(" + target + ")";
        }

        private static final long serialVersionUID = 0;
    }

    /** @see Predicates#compose(Predicate, Function) */
    private static class CompositionPredicate<A, B> implements Predicate<A>, Serializable {
        final Predicate<B> p;
        final Function<A, ? extends B> f;

        private CompositionPredicate(Predicate<B> p, Function<A, ? extends B> f) {
            this.p = checkNotNull(p);
            this.f = checkNotNull(f);
        }

        @Override
        public boolean apply(@Nullable A a) {
            return p.apply(f.apply(a));
        }

        @Override
        public boolean equals(@Nullable Object obj) {
            if (obj instanceof CompositionPredicate) {
                CompositionPredicate<?, ?> that = (CompositionPredicate<?, ?>) obj;
                return f.equals(that.f) && p.equals(that.p);
            }
            return false;
        }

        @Override
        public int hashCode() {
            return f.hashCode() ^ p.hashCode();
        }

        @Override
        public String toString() {
            // TODO(cpovirk): maybe make this look like the method call does
            // ("Predicates.compose(...)")
            return p + "(" + f + ")";
        }

        private static final long serialVersionUID = 0;
    }

    /** @see Predicates#contains(Pattern) */
    @GwtIncompatible // Only used by other GWT-incompatible code.
    private static class ContainsPatternPredicate implements Predicate<CharSequence>, Serializable {
        final CommonPattern pattern;

        ContainsPatternPredicate(CommonPattern pattern) {
            this.pattern = checkNotNull(pattern);
        }

        @Override
        public boolean apply(CharSequence t) {
            return pattern.matcher(t).find();
        }

        @Override
        public int hashCode() {
            // Pattern uses Object.hashCode, so we have to reach
            // inside to build a hashCode consistent with equals.

            return Objects.hashCode(pattern.pattern(), pattern.flags());
        }

        @Override
        public boolean equals(@Nullable Object obj) {
            if (obj instanceof ContainsPatternPredicate) {
                ContainsPatternPredicate that = (ContainsPatternPredicate) obj;

                // Pattern uses Object (identity) equality, so we have to reach
                // inside to compare individual fields.
                return Objects.equal(pattern.pattern(), that.pattern.pattern())
                        && pattern.flags() == that.pattern.flags();
            }
            return false;
        }

        @Override
        public String toString() {
            String patternString = MoreObjects.toStringHelper(pattern).add("pattern", pattern.pattern())
                    .add("pattern.flags", pattern.flags()).toString();
            return "Predicates.contains(" + patternString + ")";
        }

        private static final long serialVersionUID = 0;
    }

    /** @see Predicates#containsPattern(String) */
    @GwtIncompatible // Only used by other GWT-incompatible code.
    private static class ContainsPatternFromStringPredicate extends ContainsPatternPredicate {

        ContainsPatternFromStringPredicate(String string) {
            super(Platform.compilePattern(string));
        }

        @Override
        public String toString() {
            return "Predicates.containsPattern(" + pattern.pattern() + ")";
        }

        private static final long serialVersionUID = 0;
    }

    private static <T> List<Predicate<? super T>> asList(Predicate<? super T> first, Predicate<? super T> second) {
        // TODO(kevinb): understand why we still get a warning despite @SafeVarargs!
        return Arrays.<Predicate<? super T>>asList(first, second);
    }

    private static <T> List<T> defensiveCopy(T... array) {
        return defensiveCopy(Arrays.asList(array));
    }

    static <T> List<T> defensiveCopy(Iterable<T> iterable) {
        ArrayList<T> list = new ArrayList<T>();
        for (T element : iterable) {
            list.add(checkNotNull(element));
        }
        return list;
    }
}
